OK, I KNOW a visit to the world-class Sonoma Mission Inn and Spa is meant to be a tranquility-drenched, relaxing experience, but Sunday brunch in the resort's upscale "Restaurant" (formerly the Grille) is a little too peaceful.

We're the only people in here.

And it's a shame, because the kitchen is capable of turning out some stellar dishes, if only the interest were here. All the brunch action is at Sonoma Mission Inn's more casual Big 3 Diner. The place is packed and buzzin'. People are standing three deep in the entrance, waiting to nab a precious table in the noisy room. We don't stay. On a whim, we walk over to the recently renovated Mission Inn to check out the impressive lobby and upscale spa.

We're surprised to discover the classy restaurant inside is also serving a brunch. Three courses for $30 per person ($15 children 12 and under). While the informal (though still pricey) diner is busy with lines of people, here it's practically empty.

"The lack of people in here in no way reflects the quality of the food," apologizes the hostess as she seats us. Hmm, don't people know about the restaurant? Or is the set brunch price too steep (unlikely, since the spa treatments cost $100 to $200 a pop)? Or do dazed, overly chilled-out guests actively seek out a bit of life at the frantic Big 3 to revive their spa-induced torpor. It's all rather a mystery.

What's not a mystery is the natural elegance of the Restaurant's dining room, with its hardwood floor, rustic wrought-iron chandeliers suspended by ropes, stone counter, pots of fresh herbs on the tables, and lovely poolside views.

This Sunday's excellent brunch offers various course choices. A basket of homemade breakfast pastries--two small buttery croissants; two crumbly raisin and fennel-seed scones; a cinnamon-bran muffin and a small jar of Kozlowski strawberry jam--is a good start.

We're eager to repeat the elegant brunch experience a few weeks later, but are dismayed by a drop in quality. Once again we're about the only patrons. (With this lack in clientele, it's really no wonder interest in the kitchen and dining room is diminishing.)

The gravlax this time is a smaller portion. The server brings a hamburger instead of the sweet potato-and-multigrain burger ordered by the noncarnivore in the group. Oops. Worse, the staff abandons us, so--short of marching into the kitchen--we cannot inform anyone. When the sweet-potato burger does finally arrive, the consistency is sloppy and it lacks the promised avocado salsa.

And a roast lamb sandwich with feta cheese and mint pesto on pita bread is just a bad dish with too many intense flavors resulting in a lingering chemical taste. However, the accompanying thick, crisp french fries flecked with seasalt are perfect.

Our server tells us the Sunday brunch trend is fading, and that restaurants are increasingly having to up the ante (with free bubbly, made-to-order omelets, all-you-can-eat desserts, and other gimmicks) to lure in clientele.

I don't know if this is an accurate observation, but it would be a shame to ultimately lose the option of an elegant and leisurely Sunday brunch in such a lovely space as the Restaurant at the Sonoma Mission Inn.